典型煤质富氧着火特性试验研究

针对火电机组低负荷条件下燃烧不稳定等问题,采用哈尔滨锅炉厂有限责任公司煤燃烧特性试验炉对三种典型煤质进行不同富氧条件下的着火特性试验。试验结果表明:随着一次风氧气浓度增加,三种煤质着火温度都有所降低,但半焦(SH)着火温度降低幅度较小,而贫煤(XY)和烟煤(HB)着火温度降低幅度都呈现先大后小的趋势。此外,通过比较三种煤质着火温度,发现贫煤着火温度明显高于其他两种煤质,而烟煤除了在一次风氧气浓度为21%条件下着火温度高于半焦,其他工况下都低于这两种煤质。本次研究为今后火电机组低负荷稳燃和灵活性改造提供依据和数据。     

生物质与煤掺烧燃烧特性的实验研究

利用热重分析仪,在不同条件下,对单一生物质、煤及其混合物的燃烧特性进行分析,研究了木屑、稻壳、稻草及耒阳白沙煤的着火温度、燃烧最大速率温度和燃烬温度等燃烧特性参数。实验结果表明,生物质的着火温度比白沙煤低,生物质在燃烧过程中有两个明显的失重阶段,而煤只有一个明显的失重阶段。通过掺烧可以使生物质与煤的混合物着火温度降低,着火时间缩短,延长了整个燃烧的温度区间,使煤能更好地燃尽,使燃料的燃烧特性得到了优化。随着生物质掺混比例的提高,掺混样品着火点温度降低得更加明显;且生物质颗粒尺寸由R90变为R200时,同样的掺混比例下,尺寸R200的掺混样品着火温度更低。     

煤粉热解特性对其富氧气氛下着火机理的影响

利用非等温热重分析法对两种烟煤的热解特性及富氧下的燃烧特性进行研究.实验结果表明,煤粉中低温下的热解行为对其富氧气氛下的着火机理有明显影响.挥发分初析温度低、热解特性指数D大的煤,随着氧体积分数的增加,着火方式逐渐由非均相转变为均相.而挥发分初析温度高、D较小的煤,着火方式则无明显变化.热解活性高的煤,在着火机理转变后,着火温度显著降低,但燃尽温度基本不受影响.氧体积分数提高后两种煤粉的燃烧特性指数S都有所增大,但相同氧体积分数下不同煤种之间的S相差不多,说明着火机理的改变对S无明显影响.     

准东煤在350MW电厂锅炉内燃烧结渣特性研究

选取天池露天煤样进行研究,以昭通褐煤和大同烟煤作为对比,通过煤质分析预测准东煤结渣特性趋势。在某电厂锅炉燃烧天池露天煤,通过硅碳棒实验获得燃烧器区域渣样。研究发现,天池露天煤变形温度与软化温度均低于褐煤与烟煤,碱性氧化物含量均为最高,具有严重结渣倾向。硅碳棒结渣实验表明,由于粘性表面的形成,使得结渣速率提高。结渣样品分层分析表明,外层沉积物中石英是主要晶相,内层以钠长石为主,外层相比于内层烧结程度增加,沿生长方向处于晶体转化为非晶体过程。     

恒温下准东煤粉燃烧特性研究

针对准东煤碱金属含量高导致灰熔融温度低、在燃烧过程中容易造成沾污及结焦等问题,利用恒温热重实验系统,研究了准东煤的燃烧特性及温度、煤种掺混等对燃烧特性的影响。实验结果表明：单煤煤种燃烧过程中,不同煤种燃尽时间、燃烧速率存在显著差异,其中路茂通坎乡煤种和永华金泰煤种差异最大,路茂通坎乡煤种易着火,燃烧速率快,燃尽时间短;随着温度升高,单煤燃烧失重曲线发生左移,燃尽时间缩短,燃烧速率上升,表明温度升高会加速煤粉燃烧,并且1 000℃后提高温度对焦碳燃尽的促进作用更明显;掺混燃烧过程中,掺烧高挥发分的煤种可以有效改善煤粉燃烧初期着火特性,而掺烧高固定碳煤种可使燃尽时间延长,从而降低燃尽率;混煤掺烧能够提高灰熔点,有效改善准东煤熔融特性,从而在煤源方面减少或者避免炉膛受热面沾污、结渣,确保锅炉运行的安全性和经济性。     

CO_2浓度对煤焦燃烧及污染物排放特性影响的试验研究

在热重分析仪上进行了燃烧特性试验,考察了CO2浓度对徐州烟煤及其煤焦燃烧特性的影响,并在固定床反应器上研究了CO2浓度对烟煤燃烧过程中气态污染物排放特性的影响.结果表明:在相同CO2浓度下,随着CO2浓度的提高,煤及煤焦的着火温度略有上升,燃尽温度明显升高,煤焦的燃尽时间显著延长;SO2排放浓度随时间增加呈双峰析出,其排放量随CO2浓度的提高而减少;NO排放量随CO2浓度的提高而减少;CO排放量随CO2浓度的提高而增加;当温度低于烟煤的燃尽温度时,CO2对煤焦的气化作用使CO排放量大幅增加.     

低氧稀释条件下不同煤种着火燃烧特性实验研究

在平面火焰煤粉燃烧实验系统上研究了O2/CO2气氛中不同热协流温度(1473～1873 K)和氧气体积分数(5％～20％)下神木西烟煤、长平贫煤和济源无烟煤煤粉的着火和燃烧特性.采用光纤光谱仪和CMOS相机分别获取了煤粉燃烧的火焰辐射光谱和火焰图像,比较了不同燃烧条件下不同煤种的煤粉着火距离、颗粒温度和颗粒温度波动系数.结果 表明:随着热协流氧气体积分数的减小,煤粉火焰长度和着火距离增加,颗粒平均温度下降,颗粒温度波动系数减小;煤粉挥发分质量分数越高,颗粒温度波动系数越小,颗粒温度分布越均匀;在热协流温度为1473 K、氧气体积分数为5％的条件下,神木西烟煤的煤粉颗粒温度波动系数为2.0％,比济源无烟煤低70％,更易于实现煤粉的低氧稀释燃烧.     

纳米TiO_2催化煤燃烧的实验研究

研究了纳米TiO2在有、无CaO脱硫的工况下,对汶南褐煤和内蒙烟煤的催化燃烧效果.通过热重曲线,从着火温度、失重量、放热量等燃烧特性方面,对实验结果进行了分析.结果表明:在无CaO脱硫时,纳米TiO2使烟煤的着火温度下降15 ℃,褐煤的燃尽温度降低了32 ℃;在有CaO脱硫时,纳米TiO2使褐煤的着火温度下降17 ℃,烟煤的燃尽温度降低了8 ℃,同时褐煤、烟煤的燃烧反应活化能分别降低了5.9 kJ/mol和1.3 kJ/mol,褐煤的发热量升高.XRD图谱中没有新物质生成也证明了纳米TiO2的催化燃烧作用.这一结果为燃烧脱硫的同时,提高煤的燃烧效率,节约用煤量提供了理论依据.     

生物质与煤富氧混合燃烧特性研究

采用热重分析仪研究了棉秆、玉米芯和大同煤以及它们之间混合燃料的富氧燃烧特性。分析了富氧条件混合燃料的燃烧特征参数,如着火温度、峰值燃烧速率及其对应温度、燃尽温度及综合燃烧特性指数。采用Coat-Redfern法计算混合燃烧动力学参数。结果表明:在O2/CO2气氛下,提高氧气浓度可以改善生物质与煤混合燃料的燃烧反应,降低燃尽温度,使混合燃料的燃烧反应向低温区域移动;燃烧反应活化能在挥发分析出和固定碳燃烧的两个阶段均增大;但生物质与煤的掺混比例在30%情况下,氧气浓度的变化对混合燃料的着火温度的影响规律并不明显。在50%O2/50%CO2气氛下,随着生物质比例的增加,所有特征参数向低温区域前移,混合燃料燃烧反应活化能在挥发分析出阶段逐渐减小,在固定碳燃烧阶段逐渐增大。Coat-Redfern模型可以较好的描述棉秆或玉米芯与大同煤混合物在空气或富氧条件下的主要燃烧过程。     

陕西主要动力煤种燃烧特性的热天平研究

为了研究分析陕西主要煤种的燃烧特性,采用德国NETZSCH STA-409PC型热重分析仪分析了样品质量、升温速率、粒径对煤粉燃烧特性的影响。实验结果表明,随着粒径的减小,神木烟煤的燃烧性能先增强后变弱,粒径75～90μm左右燃烧特性最好。升温速率、样品质量对煤粉的燃烧特性也有影响。随着升温速率的提高,煤粉的着火温度升高,最大失重速率增大,最大失重速率对应的温度升高;随着质量的增加,煤粉的着火温度略有降低,燃尽温度却逐渐增大,最大失重速率明显增大,放热效应的最大温度点逐渐增大,并且煤粉挥发分燃烧低温放热与固定碳燃烧高温放热有一定的分期。     

Experimental investigation on ignition and burnout characteristics of semi-coke and bituminous coal blends

Ignition and burnout characteristics of semi-coke and bituminous coal blends were investigated by thermogravimetric analyzer and drop tube furnace. The results showed that the ignitability index and the comprehensive combustion characteristic index of the blends decrease as the blending proportion of semi-coke increases, but the average activation energy of the blends increases gradually. Ignition mode of bituminous coal is changed from homogeneous to hetero-homogeneous ignition with the increasing of semi-coke content in the blends. When the mixing proportion of semi-coke is lower than 45%, the burnout rate is lower than the weighted value in the early stage of combustion and gradually higher than the weighted value with the development of combustion process. However, the burnout is always lower than the weighted value to mix with 67% semi-coke. Increasing furnace temperature from 850 °C to 1050 °C can improve the mid-term reaction process, alleviate the negative effects of semi-coke on the co-combustion process and increase the burnout rate. So less than 45% semi-coke blending ratio and increasing furnace temperature are recommended for semi-coke and bituminous coal co-combustion.     

煤粉与生物质混燃的低温着火特性

利用自制的管式炉恒温热重测量实验台研究了掺混比、温度、煤种以及生物质种类等因素对煤粉与生物质混燃时低温着火特性的影响,并对煤粉与生物质混燃时的低温着火活化能进行了计算.结果表明:随着掺混比的增大,混合物的燃烧速率加快且燃尽程度提高;温度升高能改善煤粉与生物质混合物的燃烧特性;掺混生物质对难燃煤的着火特性影响比对易燃煤更明显;对于某一煤种,掺混水分和挥发分含量高的生物质,燃烧初期的失重速率加快;掺混灰分含量越多的生物质,在燃烧后期对煤粉的促燃作用越差;燃烧反应活化能随着生物质掺混比和温度区间的增大而减小.     

Thermal analysis and kinetics of coal during oxy-fuel combustion

The pyrolysis and oxy-fuel combustion characteristics of Polish bituminous coal were studied using non-isothermal thermogravimetric analysis. Pyrolysis tests showed that the mass loss profiles were almost similar up to 870℃ in both N_2 and CO_2 atmospheres, while further mass loss occurred in CO_2 atmosphere at higher temperatures due to char-CO_2 gasification. Replacement of N_2 in the combustion environment by CO_2 delayed the combustion of bituminous coal. At elevated oxygen levels, TG/DTG profiles shifted through lower temperature zone, ignition and burnout temperatures decreased and mass loss rate significantly increased and complete combustion was achieved at lower temperatures and shorter times. Kinetic analysis for the tested coal was performed using Kissinger-Akahira-Sunose(KAS) method. The activation energies of bituminous coal combustion at the similar oxygen content in oxy-fuel with that of air were higher than that in air atmosphere. The results indicated that, with O_2 concentration increasing, the activation energies decreased.     

Evaluation of feasibility of pelletized wood co-firing with high ash Indian coals

To reduce anthropogenic CO₂ emissions from power plants, biomass is an immediate alternative fuel which has similar properties as coal. In this regard, the present study discusses about pelletized wood (PW) co-firing with high ash Indian coal by conducting co-milling and co-firing trials in a 1000 kg/hr of pilot scale test facility. Indian coals are typically high ash content and low calorific value fuels, therefore, its interaction with coal during combustion and ash deposition have studied in detail. Based on co-milling trails of PW and coal, it was observed that as PW proportion in coal increases, the quantity of particles of size below 50 μm and as well above 500 μm were increased. From co-firing studies, it was observed that higher volatile content in PW helping in stabilizing flames while co-firing. At lower proportions, up to 10% weight PW co-firing with coal, the flame temperature and heat flux values are very close to base test of 100% coal firing. However, beyond 10% by weight of PW co-firing with coal, the flame temperature and heat flux values were increased significantly from 100% coal tests. This is because of higher calorific value of PW than coal. The CO emission was decreased with increase in PW proportion in coal but at 30% of PW in coal, CO emission was increased suddenly. However, NO and SO₂ concentrations were decreased up to 8% and 16% respectively with increase in PW proportion in coal due to lower fuel nitrogen and sulphur content in PW than coal. Analytical analysis of slagging indices suggest that the slagging potential for PW co-firing with coal is increasing as the PW proportion in coal increases.     

Comparison of bituminous coal and lignite during combustion: Combustion performance,coking and slagging characteristics

The combustion characteristics such as combustion performance, coking, and slagging—at high temperatures (700–1300 °C) of bituminous coal and lignite were investigated and compared. The results show that the ignition temperature and the activation energy of lignite are lower than those of bituminous coal, and the combustion index and the burnout index are less than those of bituminous coal. Lignite has almost no coking while bituminous coal tends to coke at high temperatures. The larger the content and reflectivity of the vitrinite, the more severe the degree of coking. In the range of 700–1300 °C, the increase of temperature has little influence on the coking characteristics of lignite and bituminous coal. The low-rank lignite has larger amounts of mineral content which tend to form low-fusion-temperature eutectics. Furthermore, there is a connection between the combustion performance, coking and slagging characteristics through the maceral compositions: the coal which is hard to ignite but easy to burn out is more likely to have strong coking ability. Meanwhile, coking tends to keep alkaline oxides stay in the char and reinforce slagging at high temperatures.     

A comprehensive biomass combustion model

A combustion model for wheat straw is discussed and compared to that of a bituminous coal, Pittsburgh No. 8. The input data into the combustion model for both cases were generated using the FG-DVC pyrolysis model, which had been validated in part experimentally. The combustion behaviour of the two fuels are investigated using a laminar flow CFD model of a drop-tube furnace. The results indicate that, because of the low calorific nature of the straw volatiles, the combustion takes place at a lower temperature, but with rapid ignition and rapid devolatilisation. The straw char is highly microporous with relatively high ash and oxygen contents; consequently, the burnout is quicker than the analogous coal char burnout.     

基于煤质变化的燃料运行分析

煤质变化会对电厂的燃料运行造成严重的影响,进行了基于煤质变化的电厂燃料运行分析.从发热量的变化、煤中灰分的变化和煤中水分的变化等方面分析了煤质变化对燃料运行的影响,并提出了相应的应对措施.     

石煤燃烧的汞排放特性研究

我国南方煤炭资源相对贫乏，而石煤的资源相当丰富，为了综合利用石煤资源，利用1MW循环流化床试验台进行了石煤和烟煤的混燃试验，对底渣、烟气和飞灰中的Hg的含量进行了详细的分析，得出了石煤和烟煤混燃的底渣、烟气和飞灰中汞的分布特性，为石煤的进一步推广应用提供依据。     

神华煤配煤的试验研究

介绍了选用榆林D矿区神华煤和平朔煤进行配煤试验,通过工业分析、灰熔点和灰成分测试分析研究混煤的灰熔融特性。掺入平朔煤能有效地改变神华煤高钙高铁的灰成分特点,提高神华煤的灰熔点。不同混配比例混煤的沉降炉燃烧结渣试验结果表明,平朔煤能降低神华煤的粘结性、熔融性和结渣趋势,且灰渣易吹落。     

Effects of coal properties on the production rate of combustion solid residue

The production rates of furnace bottom ash in a pulverized coal-fired power plant were monitored for a two-year period and its variations with respect to coal properties were analyzed. The power plant was originally designed to fire the coal sludge generated from a washing process; however, the coal sludge and its mixture with low-rank bituminous coal have been started to be used as the main fuel with time. The results of the hardgrove grindability measurements have shown that the grinding properties of sludge or its mixtures could not be predicted based on proximate analysis (moisture, ash, carbon and volatile contents); it could only be determined by experiments. The production rate of bottom ash in this particular power plant remained relatively insensitive to the high ash and moisture contents and could be estimated almost only by knowing the calorific value of the source coal. The evaluated dependency was linear.